Attention: TDR Forum Junkies Spent some quality time huggin my Cummins this weekend after discovering a puddle of diesel under the engine. The culprit was the rubber return line from the injection pump. I learned a lot reading the many TDR posts on this subject, then learned a lot more when I waded into the job. Since this is such a common repair I thought I'd gather everything together in one post for the benefit of those who will be facing this problem in future.
1. Although there are many places where leaks can develop (fuel heater electrical connection, banjos atop fuel filter, metal lines where mounting brackets are welded on, etc. ), the short sections of rubber feed and return hose are very common failure points. If you haven't replaced yours yet, lay in an emergency supply of good marine diesel hose and stainless steel clamps (from any good marine supply shop or http://www.fostertruck.com/dodge/default.htm). I bought mine months ago, and was right proud to have 'em on hand when my truck went down on a weekend.
2. There are a million places where a leak might develop, and all of them are hard to reach, so the key to getting the job done right the first time is to visually observe the leak before you go tearing into the job. This is, however, easier said than done. There will probably be fuel all over everything on the left side of the engine block, so the pattern of wetness won't tell you much. With the engine running (and a fire extinguisher close at hand) I observed carefully with a million-candlepower flashlight, and could see a shower of droplets coming from under where the intake manifold forms a sort-of shelf just inboard of the injection pump. This narrowed down the possibilities to either the the steel-to-rubber junction on the return line (which was the culprit) or else the steel line itself coming off of the injection pump (which some folks have observed can develop a crack where the mounting bracket is welded on).
3. Replacing the return hose isn't any fun, but it also isn't near as bad as you might conclude from reading all the TDR posts on this subject. Essential tools include:
a. a mechanics inspection mirror on a long arm, so you can see what you're up against. Once you've laid an eyeball on the task your fingers can do all the rest.
b. a 9/32" socket with a short extension, on a small 1/4" drive ratchet (to loosen the existing hose clamps).
4. To replace the return hose, start by moving everything that's in your way. This takes only a few minutes, and greatly simplifies the task. This includes:
a. Intake air horn (remove). There are five bolts, which want a 10 mm socket on a short extension... some are long bolts and some are short. There's also a 10 mm bolt securing the oil dipstick tube to the intake. Loosen the bottom hose clamp from the rubber boot attaching the intake to the charge air tube (with a 7/16" deep socket). Once you've removed the intake mounting bolts, just rotate the assembly 90 deg. on the air tube, then pull it off. Stuff a clean rag in the air tube and put some Saran Wrap or something over the intake air heater.
b. Rear engine hoist point (remove)
c. Master cylinder (pull off of two mounting studs and lean it over toward the driver's fender; you don't need to disconnect the brake lines)
d. Fuel shutoff and heater solenoids (held by one sheet metal screw under the rubber hood gasket; leave their wires connected and just move them out of the way)
e. The big vacuum hose that attaches just behind the master cylinder
f. Fuel filter (remove)
g. Disconnect the big wiring harness plug that's in your way.
h. Starter (remove). The nut attaching the fat cable that comes from the battery wants a 15 mm socket. The nut attaching the thin wire wants a 5/16" socket on a 1/4" drive. The three funny-looking bolts that attach the starter to the engine block want a 10 mm 12-point box-end wrench. The starter is heavier than you would expect... don't drop it on your face.
Note that some have said you can gain access by removing the front left wheel well liner. I didn't try this because in my case it didn't look promising.
5. Now with an inspection mirror and bright flashlight you can easily visualize the clamp attaching the hose to the short metal tube coming off of the injection pump. You can reach this clamp either by laying on top of the engine or - less painfully - from beside the left fender while standing on a short stepladder (if you're a runt like me).
6. My clamp was real loose... it might have been this looseness, rather than a hose failure, that was causing my problem; I don't know. In a roadside emergency situation I might have just tried tightening this clamp if I didn't have any replacement hose with me. But if you can replace the hose, do.
7. Using the 9/32" socket on a quarter-inch ratchet, loosen the hose clamp. In my case, a firm, patient pull on the hose slowly slipped it off of the metal tube. Your mileage may vary, in which case use a utility knife to split the end of the hose.
8. You can see and reach the other end of the hose from under the truck, with your head where the starter used to be. Laying on a creeper I could just reach this clamp. Again, a firm steady pull popped it off of the metal tube.
9. Still from underneath the truck, with a needlenose plier pry open the bracket that secures the middle of the hose, and remove the hose. Don't be discouraged if the hose looks perfectly fine... mine did, but it was the source of the leak.
10. Still from underneath the truck, feed the new hose through the retainer bracket and up toward the engine... piece of cake! Slip the bottom end of the hose onto the metal line that runs to the fuel tank. Clamp 'er down good'n tight... the marine diesel hose needs and wants a lot of clamp pressure.
11. While you're down there under the truck, replace the corresponding feed hose, too (its right beside the hose you just replaced). This one's easy; you can see and reach both clamps from under the truck with the starter removed.
12. Install a new fuel filter (I prolly could have re-used the old one... it had only 3,000 miles on it... but my filter wrench leaves a slight dent in the filter's side, so I was superstitious about re-using it). Loosen the tiny bleed screw atop the front-most banjo bolt on the top of the filter mount, and pump the priming button (under the lift pump) 150 times or until fuel starts streaming out from around the bleed screw. Some folks swear by using a length of broom handle to pump this button, but I find this to be more trouble than its worth... just suck it up and pump! Tighten the bleed screw (it doesn't take much torque).
13. Mop up the engine block as best you can, then put everything back together. Take a wire brush to the threads of the five bolts that attach the intake air horn, then apply a thin coat of RTV to the threads before reinstalling. Torque these bolts to 18 ft-lb. I finally got around to installing new gaskets above and below the intake air heater (six bucks at the dealer), and I'm glad I did... gained 3 PSI of boost! Check your brake fluid level... my reservoir leaks when I lay the master cylinder over to the side.
14. Crank on the engine... it'll have to think about it for a while before it starts up, but it should start. Don't crank the starter for more than 30 seconds at a time, with 2-minute cool-downs in between these sessions. I've never needed to crank for more than 10 or 15 seconds before the Cummins wakes up.
15. With the engine running, inspect for leaks again with a bright flashlight. When you don't see any, smile and go get yourself a beer.
1. Although there are many places where leaks can develop (fuel heater electrical connection, banjos atop fuel filter, metal lines where mounting brackets are welded on, etc. ), the short sections of rubber feed and return hose are very common failure points. If you haven't replaced yours yet, lay in an emergency supply of good marine diesel hose and stainless steel clamps (from any good marine supply shop or http://www.fostertruck.com/dodge/default.htm). I bought mine months ago, and was right proud to have 'em on hand when my truck went down on a weekend.
2. There are a million places where a leak might develop, and all of them are hard to reach, so the key to getting the job done right the first time is to visually observe the leak before you go tearing into the job. This is, however, easier said than done. There will probably be fuel all over everything on the left side of the engine block, so the pattern of wetness won't tell you much. With the engine running (and a fire extinguisher close at hand) I observed carefully with a million-candlepower flashlight, and could see a shower of droplets coming from under where the intake manifold forms a sort-of shelf just inboard of the injection pump. This narrowed down the possibilities to either the the steel-to-rubber junction on the return line (which was the culprit) or else the steel line itself coming off of the injection pump (which some folks have observed can develop a crack where the mounting bracket is welded on).
3. Replacing the return hose isn't any fun, but it also isn't near as bad as you might conclude from reading all the TDR posts on this subject. Essential tools include:
a. a mechanics inspection mirror on a long arm, so you can see what you're up against. Once you've laid an eyeball on the task your fingers can do all the rest.
b. a 9/32" socket with a short extension, on a small 1/4" drive ratchet (to loosen the existing hose clamps).
4. To replace the return hose, start by moving everything that's in your way. This takes only a few minutes, and greatly simplifies the task. This includes:
a. Intake air horn (remove). There are five bolts, which want a 10 mm socket on a short extension... some are long bolts and some are short. There's also a 10 mm bolt securing the oil dipstick tube to the intake. Loosen the bottom hose clamp from the rubber boot attaching the intake to the charge air tube (with a 7/16" deep socket). Once you've removed the intake mounting bolts, just rotate the assembly 90 deg. on the air tube, then pull it off. Stuff a clean rag in the air tube and put some Saran Wrap or something over the intake air heater.
b. Rear engine hoist point (remove)
c. Master cylinder (pull off of two mounting studs and lean it over toward the driver's fender; you don't need to disconnect the brake lines)
d. Fuel shutoff and heater solenoids (held by one sheet metal screw under the rubber hood gasket; leave their wires connected and just move them out of the way)
e. The big vacuum hose that attaches just behind the master cylinder
f. Fuel filter (remove)
g. Disconnect the big wiring harness plug that's in your way.
h. Starter (remove). The nut attaching the fat cable that comes from the battery wants a 15 mm socket. The nut attaching the thin wire wants a 5/16" socket on a 1/4" drive. The three funny-looking bolts that attach the starter to the engine block want a 10 mm 12-point box-end wrench. The starter is heavier than you would expect... don't drop it on your face.
Note that some have said you can gain access by removing the front left wheel well liner. I didn't try this because in my case it didn't look promising.
5. Now with an inspection mirror and bright flashlight you can easily visualize the clamp attaching the hose to the short metal tube coming off of the injection pump. You can reach this clamp either by laying on top of the engine or - less painfully - from beside the left fender while standing on a short stepladder (if you're a runt like me).
6. My clamp was real loose... it might have been this looseness, rather than a hose failure, that was causing my problem; I don't know. In a roadside emergency situation I might have just tried tightening this clamp if I didn't have any replacement hose with me. But if you can replace the hose, do.
7. Using the 9/32" socket on a quarter-inch ratchet, loosen the hose clamp. In my case, a firm, patient pull on the hose slowly slipped it off of the metal tube. Your mileage may vary, in which case use a utility knife to split the end of the hose.
8. You can see and reach the other end of the hose from under the truck, with your head where the starter used to be. Laying on a creeper I could just reach this clamp. Again, a firm steady pull popped it off of the metal tube.
9. Still from underneath the truck, with a needlenose plier pry open the bracket that secures the middle of the hose, and remove the hose. Don't be discouraged if the hose looks perfectly fine... mine did, but it was the source of the leak.
10. Still from underneath the truck, feed the new hose through the retainer bracket and up toward the engine... piece of cake! Slip the bottom end of the hose onto the metal line that runs to the fuel tank. Clamp 'er down good'n tight... the marine diesel hose needs and wants a lot of clamp pressure.
11. While you're down there under the truck, replace the corresponding feed hose, too (its right beside the hose you just replaced). This one's easy; you can see and reach both clamps from under the truck with the starter removed.
12. Install a new fuel filter (I prolly could have re-used the old one... it had only 3,000 miles on it... but my filter wrench leaves a slight dent in the filter's side, so I was superstitious about re-using it). Loosen the tiny bleed screw atop the front-most banjo bolt on the top of the filter mount, and pump the priming button (under the lift pump) 150 times or until fuel starts streaming out from around the bleed screw. Some folks swear by using a length of broom handle to pump this button, but I find this to be more trouble than its worth... just suck it up and pump! Tighten the bleed screw (it doesn't take much torque).
13. Mop up the engine block as best you can, then put everything back together. Take a wire brush to the threads of the five bolts that attach the intake air horn, then apply a thin coat of RTV to the threads before reinstalling. Torque these bolts to 18 ft-lb. I finally got around to installing new gaskets above and below the intake air heater (six bucks at the dealer), and I'm glad I did... gained 3 PSI of boost! Check your brake fluid level... my reservoir leaks when I lay the master cylinder over to the side.
14. Crank on the engine... it'll have to think about it for a while before it starts up, but it should start. Don't crank the starter for more than 30 seconds at a time, with 2-minute cool-downs in between these sessions. I've never needed to crank for more than 10 or 15 seconds before the Cummins wakes up.
15. With the engine running, inspect for leaks again with a bright flashlight. When you don't see any, smile and go get yourself a beer.
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The only other gasket I see in the area is the one between the intake manifold (part of the head) and the manifold cover, which houses the intake heater and requires removal of the high-pressure injector lines to remove it. 
